"I want to apologise to Mrs (Anne) McCabe and the McCabe family, and to Garda Ben O'Sullivan and to the families of other members of the state forces who were killed by republicans in the course of the conflict, " said Mr Adams.
Among the marchers were former EastEnders actress Brooke Kinsella, whose 16-year brother Ben was stabbed to death in June, and Caroline Kingonzila, mother of promising footballer Oliver who was killed last Saturday.